If read-out errors occur due to magnetic instability of a magnetic read head when a recording signal is read out in a magnetic disk device, such as a hard disk drive (HDD), an error recovery process is performed to return the magnetically unstable read head to a stable state by repeatedly performing off-track processing and dummy writing and varying the read-out current/voltage to impart thermal and magnetic stress to the read head, as shown in FIG. 6.
However, a problem occurs in that as magnetic read heads have transitioned from being primarily anisotropic magnetoresistive (AMR) and giant magnetoresistive (GMR) heads to being primarily tunneling magnetoresistive (TMR) heads, the resistance of the magnetic read head increases by at least one order of magnitude, which causes Joule heat generated by the application of a read-out voltage of the same magnitude to decrease by at least one order of magnitude, and consequently there is insufficient thermal stress to return the magnetically unstable read head to a stable state. This can be visualized as Read Head Heat Generation Amount ∞ (Applied Voltage)2/(Read Head Resistance).